Packings for pumps, valves, and the like

ABSTRACT

A packing for fluid-tightly sealing movable elements of pumps, valves, and the like. The packing comprises an inner Teflon-(a trade mark hereinafter referred to as TFE) containing core and an outer carbon-containing jacket surrounding the core. This core may be made of TFE fiber or of a TFE-impregnated packing material such as asbestos or fiberglass, while the outer jacket can be composed of graphite filament either wrapped or braided around the core.

United States Patent Zumeta et al.

PACKINGS FOR PUMPS, VALVES, AND THE LIKE Inventors: Julio Zumeta, NewYork, N.Y

Edward M. Case, Weston, Conn.

Assignee: The Marlo Company, Inc., New

York, NY.

Filed: May 7, 1971 Appl No.: 141,448

Related US. Application Data Continuation of Ser. No. 688.806, Dec. 7,1967, abandoned.

US. Cl. 277/230 Int. Cl F16j 15/10 Field of Search]; 277/227, 228,229,230, 231,

277/232, DIG. 3; 156/293, 301, 311

References Cited UNITED STATES PATENTS 9/1955 Jelinek 156/311 Feb. 12,1974 Lewis 277/D1G. 3 Moore 277/230 X Primary Examiner-Louis R. PrinceAssistant ExaminerRobert 1. Smith Attorney, Agent, or FirmBlum,Moscovitz, Friedman & Kaplan A packing for fluid-tightly sealing movableelements of pumps, valves, and the likel The packing comprises an innerTeflon-(a trade mark hereinafter referred to as TFE) containing core andan outer carboncontaining jacket surrounding the core. This core may bemade of TFE fiber or of a TFE-impregnate'd packing material such asasbestos or fiberglass, while the ABSTRACT outer jacket can be composedof graphite filament ei- I ther wrapped or braided around the core.

7 Claims, 2 Drawing Figures WRAPPED CARBON (GRAPH/ATE) FIBER (F/LAMEN'T)JACKET TFE FIBER CORE PMENI UFEB 1 2 I974 WRAPPED CARBON (GRAPH/TE)FIBER (F/LAMENT) JACKET TFE FIBER CORE BRAIDED JACKET OF CARBON(GRAPH/TE) F/LAMENT CORE OF TF E IMPRE GNATED v PACK IN G INVENTORSJUL/O ZUMETA BY EDWARD M. CASE 1 PACKINGS FOR PUMPS, VALVES, AND THELIKE BACKGROUND OF THE INVENTION This application is a continuation ofapplication Ser. No. 688,806 filed Dec. 7, 1967, now abandoned.

The invention relates to packings for fluid-tightly sealing movablecomponents of pumps, valves, and the like.

Conventional packings of this type include two important categories. Oneof these categories is Teflon packings, including those made of pure TFEfiber as well as those made of other fibers to which is added a TFEdispersion, resulting in a TFE-impregnated structure. The otherimportant category includes packings made of carbon such as graphitefiber or filament.

Each of these categories has its own inherent drawbacks.-

Thus, in the case of TFE packings, it is well known that unlessconsiderable care is taken in the installation of such a packing, asintering effect on the TFE wearing surface occurs. This effect, as aresult of the rapid build-up of heat under frictional rod contact, forexample, which is further accelerated by sealing take-up (and which is aresult, also, of poor heat transmission properties of Teflon) results ina hard-abrasive surface causing the moving rod or shaft to wear rapidlyand resulting in packing burn-out. As a result of these inherentlimitations, all packing manufacturers, under advice given by E. l.DuPont de Nemours Inc., instruct TFE packing users to install thepacking with very great care so as to avoid heavy take-up and to permita lubricating seepage or drip through the stuffing box at all times. Inthe absence of such seepage or drip of the lubricant packing bum-outwill occur.

These limitations prevent TFE packings from being used effectively,since in many toxic, noxious, explosive, or severely corrosiveapplications it is highly desirable, if not essential, to have acompletely dry and leakproof packing installation.

Graphite filament packing, on the other hand, while it does not have theundesirable sintering properties of TFE packings, will bum-outparticularly under operating conditions of high temperature, if there isexcessive compression at the stuffing box. It is well known that in thecase of graphite filament packings it is difficult to avoid excessivecompressions. One reason for this difficulty results from the compactingquality of the graphite filament packing. This latter quality gives thegraphite filament packing a lack of resiliency or bounce" (in itself adeficiency in terms of sealing effectiveness with respect to a movingrod or shaft or misaligned valve stem) with a resulting lack offeel inthe compressive or take-up procedure. Thus, as a practical matter anoperator cannot determine from the resistance of the packing whensufficient take-up pressure has been exerted in normal installation ormaintenance operations.

This lack of feel with such packings, the development of which feel isan essential and well known factor in the training and efficiency ofmaintenance engineers and mechanics, is in sharp contrast with the feelwhich can be obtained in virtually all other widely used conventionalpacking materials such as asbestos, flax, lead, etc. This inherent lackof resistance thus will frequently result in burning-out of graphitefilament packing owing to overcompression which cannot be avoided.

On the other hand pure graphite filament packing material is inherentlyporous. It has voids between the strands, and in order to provide aproper seal frequent adjustments of the compression of the packing arerequired. Inasmuch as such compression, for the reasons set forth above,is difficult to regulate, there is an inherent lack of denseness in thistype of packing, resulting in installation and maintenance procedureswhich are inherently unfavorable for continuous successful operation.

SUMMARY OF THE INVENTION It is thus a primary object of the presentinvention to provide a packing of the above general type which willavoid the drawbacks inherent in the above categories of packing.

In addition, it is an object of the invention to provide a packing whichwill retain the virtues of the above categories of packings.

Thus, it is a more specific object of the present invention to provide apacking which will combine the inherent virtues of a Teflon type andcarbon type of packing in such a way that the virtues of one of thesetypes will complement the virtues of the other while at the same timeneutralizing the above-described inherent deficiencies of each type ofpacking by the beneficial effects resulting from the combination of theinvention.

The above objects are achieved with the present invention by providing apacking which includes an inner Teflon-containing core and an outercarbon-containing jacket which surrounds the core. Thus, the core of thepacking of the invention can be made either of TFE fiber, TFE strands orsome type of commonly used TFE- impregnated packing material, such aswhite asbestos, blue asbestos, fiberglass, etc., or some TFE filledmaterial, and about this core there is an outer carboncontaining jacketof graphite filament, for example, which may be braided about the innercore or which may be wrapped about the inner core, or other means offorming a jacket besides braiding may be used.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is bad to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a schematic fragmentary partly sectional illustration of onepossible embodiment of a packing of the invention; and

FIG. 2 is a schematic partly sectional fragmentary illustration ofanother embodiment of a packing of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings, it willbe seen that the embodiment of FIG. 1 includes a core 10a made of TFEfiber while in the embodiment of FIG. 2 the core 10b is made ofTFE-impregnated packing material. As was indicated above, this packingmaterial may be, for example white asbestos, blue asbestos, fiberglass,etc. The fiber core 10a of FIG. 1 may be bleached Teflon TFEfluorocarbon available from the duPont Company as number 4050-540 (4050denier, 540 filament), and these fibers are twisted into a bundle whichforms the core a.

In the case of FIG. 2, the TFE-impregnated packing may, for example,take the form of 30 to 45 weight per cent polytetrafluoroethylene in theform of impregnation for a braided glass fiber core, for example. Theamount of Teflon impregnating the packing material of the core 10b canof course be varied, and the impregnating polytetrafluoroethylenepolymer is in nonfibrous form and in the uncured state. In FIG. 1 thecore 10a is polytetrafluoroethylene in fibrous form.

Braided glass fibers which form the core 10b of FIG. 2, for example, maybe immersed in a polytetrafluoroethylene (Teflon) dispersion identifiedas TD-3 by duPont which contains approximately 60 percent by weightTeflon, 6 percent (by weight of Teflon) wetting agent and the remainder,water. For a one half inch packing the time of immersion may be 2minutes and the packing is then air dried and calendered to size.

In FIG. 1 the core 10a is surrounded by a carbon jacket 12a in the formof suitable graphite filament which is wrapped around the core. In FIG.2, however, the carbon jacket 12b is in the form of braided carbonfilament.

Thus, the jackets 12a and 12b are made of carbon filament in graphiticform, inasmuch as graphite filaments are stronger than carbon filamentsin other forms. The graphite filaments may be in the form of graphiteyarn GY-2-l0 (high twist) available from the Carborundum Company,Sanborn, N.Y. However, other suitable carbon filaments may be used.

With the above-described structure of the invention it is possible touse, without attenuating or reducing its anti-corrosive effectiveness, apacking which is in its largest mass either Teflon or TFE-impregnated,without making it essential to provide for seepage or drip through thestuffing box in order to avoid sintering and consequent burn-out. In thepast it would always have been feasible to cover a TFE core of any typewith a non-TFE material. However, such an expedient would have negatedthe very purpose for which the TFE is employed, since if such a coveringcould resist the chemical attack encountered in a given application, theTFE component would not be required, and if the covering could notresist such an attack then it would quickly be destroyed and the TFEstructure would then be the active mechanical agency and would besubject to the deficiencies described above. It is only with thedevelopment of carbon in the form of graphite yarn, for example, that amaterial substantially equal to TFE in chemical resistance on virtuallyall applications has been available to thus make it possible to containan effective sealing core of TFE in some form.

As a result of the heat-conducting characteristics of graphite filament,at any given temperature more heat will be conducted away from thepacking through the wall of the stuffing box than would be possible withany form of TFE packing unaccompanied by the graphite filamentcomponent. The result is an elevation in the effective temperature limitat which TFE can be used in a stuffing box. The effective limit of TFEalone is determined by the point at which the sintering effect occurs.However, the sintered product retains its structural integrity and couldbe utilized until a higher temperature is reached, if it were not forthe undesirable effect of the hard-sintered product on a movingcomponent such as a pump shaft. Inasmuch as the graphite filamet jacketretains its anti-frictional properties and is not affected by elevatedtemperatures, it effectively separates any interior sintering of thecore from engagement with the moving shaft and thereby prevents theabove-mentioned injurious effects and prolongs the life both of thepacking and of the moving shaft or other moving component.

Furthermore, the interior core 10a or 10b provides a dense, moreresilient internal structure which eliminates the difficulties anddangerous consequences of a packing composed entirely of graphitefilament, as set forth above. In this way it is possible to providebetter control and regulation of the installation and the seatingpressures can be controlled with a high degree of accuracy, reducing thepossibility of packing failure and shaft damage. Thus, the desirableanti-frictional and heat-transmitting characteristics of graphitefilament are retained while the negative characteristics of porosity andlack of resiliency thereof are eliminated.

In addition, the packing of the invention is much less expensive than apure graphite filament packing inasmuch as at the present time the costof graphite filament is approximately $40.00 per pound, as opposed to acost of approximately $8.25 per pound for pure TFE fiber andapproximately $2.50 per pound for other TFE impregnated core materials.

Inasmuch as the completely finished packing of the invention, whateverthe core material may be, will contain only a relatively smallpercentage of graphite filament by weight, the packing will provide avery substantial cost saving to the consumer.

What is claimed is:

1. A packing for fluid-tightly sealing movable elements of pumps,valves, and the like, comprising an inner resilient core made of afibrous material selected from the group consisting of Teflon,Teflonimpregnated fiberglass, and Teflon-impregnated asbestos, and anouter jacket surrounding and directly engaging said core for enclosingthe latter, said jacket having the form of a tubular body of filamentarygraphite and having a thickness great enough to conduct away asubstantial portion of whatever heat is generated when said jacket is incontact with a movable element, thereby protecting said resilient corefrom thermal degradation.

2. The packing of claim 1 and wherein said core is made of braidedTeflon-containing packing material.

3. The packing of claim 2 and wherein the packing material is asbestos.

4. The packing of claim 2 and wherein the packing material isfiberglass.

5. The packing of claim 1 and wherein the jacket is graphite filament.

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2. The packing of claim 1 and wherein said core is made of braidedTeflon-containing packing material.
 3. The packing of claim 2 andwherein the packing material is asbestos.
 4. The packing of claim 2 andwherein the packing material is fiberglass.
 5. The packing of claim 1and wherein the jacket is made of graphite filament.
 6. The packing ofclaim 1 and wherein said jacket is braided around said core.
 7. Thepacking of claim 1 and wherein said core is a Teflon-containing asbestosand said jacket is a braided graphite filament.